118 A YEAR IN SCIENCE 



minutes, and will make the water safe to drink. If 

 this quantity makes the water taste, use a little less, 

 otherwise not. Get the chloride of lime in metallic 



Questions 



1. Is water an element or a compound? 



2. In what two ways can this be shown? 



3. How long has this fact been known? 



4. Give the chemical formula for water. 



5. Name the most essential physical properties of 

 water. 



6. How does water differ from most substances 

 when cooled below 4 C C. ? 



7. Of what advantages is this peculiarity in 

 nature's plan? 



8. How do you account for the "fluffed up" 

 appearance of the garden soil early in the spring? 



9. How does water help to enrich the soil? 



10. What is meant by hard water? 



11. How may hard water be rendered soft? 



12. Explain fully the role of water in the life of 

 most plants and animals. 



13. What danger is there in drinking surface 

 water ? 



14. Of what advantage is filtered water? 



15. Why is it necessary to clean the filter 

 frequently ? 



16. How may water that is under suspicion, be 

 rendered safe for drinking purposes? 



17. Why should the citizens of a community heed 

 carefully the warnings of the Board of Health or the 



